Compact Water/Water Heat Pump Core, and Heat Pump Comprising Same

ABSTRACT

The whole set includes a compressor assembly ( 10 ), inlet ( 23 ) and outlet ( 24 ) to and from a harnessing loop, inlet ( 33 ) and outlet ( 34 ) to and from a heating loop, and two heat exchangers ( 20, 30 ), coupled to the compressor assembly and to the inlets and outlets. Linking pipes ( 21, 22, 31, 32 ) between heat exchangers and the compressor assembly, and/or inlets and outlets from and to harnessing and heating loops, are not linking pipes assembled by brazing but are welded stainless steel pipes, notably by orbital TIG welding. The whole set is enclosed in a tighten enclosure ( 40 ) comprising a supporting base ( 41 ) and a bonnet ( 42 ) sealed together.

The invention is related to water loop heat pumps.

Such equipment allows to harness thermal energy available in air, earth upper layers or free water, concentrate this energy and supply it in this form (at higher temperature) to hot water central heating.

“Water loop” heat pump means an equipment in which the harnessing loop as well as the heating loop are both filled by a liquid. It differs from “water/air” or “air/air” equipments. It must be considered that, following need, the water can be replaced or completed by an other liquid. For instance, in the harnessing loop. To the water in this loop, ethylene-glycol or other additive is most often added as antifreeze.

Interest in the use of a heat pump lays in its principle according which the energy necessary to feed it is lower than the heating energy it delivers. To express this capacity it is considered a “performance coefficient” (COP) ratio between energy delivered and energy absorbed by the system. This ratio can typically reach 5 in the best equipments presently available.

More precisely, a heat pump is composed of a compressor assembly and two heat exchangers linked one to the harnessing loop and the other one to the heating loop. The exchangers are, on the other side, linked to the compressor assembly, one to its hot point and the other one to its cold point. Inside the compressor assembly is found a condenser, an expander and a vaporiser. The compressor concentrates the harnessed energy at the condenser side and disperses its cold into the harnessing loop at the vaporiser side.

The overall performance of the heat pump is best when thermal exchange is optimised and action of the compressor and exchangers is conducted in best possible thermal insulation from external atmosphere.

The compressor, its internal cooling gas, as well as the two heat exchangers, are linked into a one and same functional assembly, hereunder expressed as “water loop heat pump core”. This assembly forms a set that is in turn linked to manifolds for the harnessing and the heating (pipes, circulating pumps, thermal captors, etc.) as well as to supplies and regulation of the whole system.

The heat pumps supplied up to now are formed with internal connections by piping that is performed by methods usual to technicians specialised in cooling and heating equipment.

More precisely links between compressor and exchangers, as well as between exchangers and inlets/outlets of harnessing and heating loops, are brass pipes connected by brazing.

However, in heat pumps, the use of brass pipes and the connection by brazing, is not without introducing drawbacks.

First, brass is characterized by a high thermal conductivity, which is not favourable in this application since it can result in parasitic thermal exchanges with environment.

Second, connections by brazing, if they are rightly leak free, are not of a great mechanical strength and can be submitted to corrosion. As it is well known, brazing consists in assembling two different metals by the mean of a third one (silver for instance when performance is requested) heated up to above its fusion point. Since compressor are made of steel and the exchangers of steel or stainless steel, and these parts linked by brass pipes, in all brazed links are observed changes of metal:steel/brass or stainless steel/brass, and third metal in addition.

These links are submitted, from the compressor, to vibrations that would quickly lead to leaks or even breakages in case of a design too stiff.

To avoid this drawback, brass pipes are usually designed in order that suppleness is granted in the manifold. This is obtained by the use of pipes of greater length and/or of adapted geometry (lyres, spires, etc.) that absorb mechanical stress, mostly the transfers of vibrations.

Such increase of pipe length brings however an increase of the surface of exchange with ambient atmosphere, and so losses of the usable energy, and as well, increases the volume of the gas used by the compressor.

The present invention aims to overcome these drawbacks, by introducing a water loop heat pump core optimised in performance as in compactness and reliability.

The water loop heat pump core of the invention follows the general description above, that is including, more precisely and in a way known in itself: a compressor assembly including a close circuit filled with cooling gas with compressor, condenser, expander and vaporiser; inlet and outlet on the hot side, inlet and outlet on the cold side; a first exchanger coupled by its primary side to the vaporiser of the compressor assembly and by its secondary side to the harnessing loop; and a second exchanger coupled by its primary side to the condenser of the compressor assembly and by its secondary side to the heating loop.

In a manner characteristic of the invention, the linking pipes between the exchangers and the compressor assembly, and/or the linking pipes between the exchangers and the inlets/outlets to and from harnessing and heating loops, are non-brazed linking pipes, made from welded stainless steel pipes.

By replacing brass tubes, used until now, by stainless steel pipes, and by connections not by brazing but by welding, the links in the water loop heat pump core of the invention do not present solution of continuity any more, that introduces a quality in mechanical resistance—notably to vibrations—and a quality in resistance to corrosion incomparably higher to what they used to be with brass tubes and brazing.

It is well known that welding, when rightly performed, is equivalent in terms of mechanical strength and tightness to what is the original pipe.

Especially, the vibrations emitted by the compressor cannot introduce breakage of such links, and the mechanical strength, the geometry and the suppleness of the stainless steel pipes and exchangers can be designed in order to absorb such vibrations in short and small diameter circuits, all that being impossible to brass tubes used up to now.

This reduction in size allows to decrease in the same proportion the parasitic thermal exchanges between the gas and environment, and thus losses of energy, as well as the volume of gas necessary to the equipment. On top of this reduced exposure, the parasitic thermal exchanges will also be reduced by the fact that steel has a far lower thermal conductivity than brass and that no fastening to a frame is necessary any more to hold the exchangers. By this last advantage, thermal bridges between exchangers and outside atmosphere will be suppressed.

It is thus possible to notably increase the performance coefficient of the heat pump, typically of 1 to 2 points, what means that it become possible to reach COP in the range of 6 to 7, far above performance of the best equipments presently available.

The necessary welding of pipes is favourably performed by orbital TIG welding, a perfectly mastered process that can be automated, thus with a precise control of the necessary parameters and an excellent reproducibility, leading here again to increase the reliability of the equipment. Moreover, orbital TIG welding allows to keep down the temperature increase of the compressor body during the process of welding, thus avoiding to weaken it.

The exchangers will preferably be stainless steel tubular exchangers. Such exchangers, perfectly fitted to a heat pump core following the invention in which all links are welded stainless steel pipes, may advantageously replace plate exchangers assembled by brazing, which are most often used in standard heat pumps. Even if they grant a good thermal exchange, plate exchangers are fragile and more sensible to water loaded with minerals that can introduce blockages by deposition or introduction of impurities. Last, their mechanical strength is limited, especially when exposed to continual vibrations.

Thanks to the considerable increase of reliability, it is not necessary any more to keep access to internal parts of the heat pump core after original production. All these parts (compressor assembly, heat exchangers, linking pipes between exchangers and compressor and linking pipes between exchangers and inlets/outlets to and from harnessing and heating networks) can thus be confined in an enclosure that forms an unique, tighten and insulated, functional set.

This tighten enclosure can favourably be composed of a supporting base receiving the compressor assembly and pipe-links to the exchangers, and a bonnet covering them, the supporting base and the bonnet being joined in a manner that is permanent, for instance by welding if they are of metal.

It should be understood that the aforesaid “supporting base” may form whole or a part of any side or of certain sides of the assembly, not only the lower part thereof.

The remaining free space inside the enclosure can be filled by an isolating material, the supporting base being then equipped by an appropriate occlusive aperture to introduce this isolating material.

Vacuum can be applied to the internal atmosphere of the enclosure, or it can be filled by appropriate dry isolating gas, the supporting base being then equipped by an appropriate occlusive aperture, opening to this atmosphere, in order to apply vacuum or introduce the gas.

Preferably, the inlets and outlets of the harnessing loop and the heating loop, as well as the occlusive apertures are all grouped on the supporting base.

The invention shall also encompass, as such, a heat pump including, in combination, a pump heart as set forth above which co-operates with coupling members, including at least one circulating pump, to a harnessing loop, coupling members, including at least one circulating pump, to a heating loop, thermal regulating means, and means for supplying electricity to the assembly.

We shall now describe an example of water loop heat pump core built following the teaching of the invention, with reference to the unique 3D schematic diagram in annex, that presents the constitutive parts of this heat pump core.

In the drawing, the reference 10 shows the compressor assembly, that is a set with close circuit filled by gas, including a compressor 11, a vaporiser 12, a condenser 13 and an expander 14. The motor of the compressor is, for instance, an electric motor powered by a line coming from outside the enclosure and linked to public electric network.

A first heat exchanger 20 is coupled on its primary side to vaporiser 12 of the compressor assembly 10, through two links 21 and 22. On its secondary side, it is linked to inlet 23 and outlet 24 to be in turn linked to a harnessing loop; links to openings 23, 24 are insured by pipes 25, 26.

A second heat exchanger 30 is coupled on its primary side to the condenser 13 of the compressor assembly 10 through two links 31 and 32.

On its secondary side, it is linked to inlet 33 and outlet 34 from and to the heating loop; links to opening 33, 34 are insured by pipes 35, 36.

The exchangers 20 and 30 are favourably stainless steel welded tubular twisted exchangers, the size of which is designed according to the compressor nominal power in order that they grant optimum exchange both to the heating and from the harnessing, loops.

In a characteristic manner of the invention, the links 21, 22, 31, 32 between the compressor 10 and the heat exchangers 20 and 30, as well as the links 25, 26, 35, 36 between the exchangers 20 and 30 and inlets 23, 33 and outlets 24, 34, to and from the harnessing and the heating loops, are insured by means of welded stainless steel pipes. The diameter of these pipes is optimised in order that this link, without perturbing the transfer of fluids (gas, or fluid circulating in the loops), with a length and a geometry designed to perform this link by the shortest possible way.

Moreover, thanks to the excellent mechanical strength of the welded links, the exchangers can be merely supported by the pipes 21, 22, 25, 26 (or 31, 32, 35, 36, on the other side), that keep them in place without necessity of holder of any sort attached to a frame that would generate thermal bridges.

A small diameter pipe 16, that can be of stainless steel as well, in spiral or multi-spiral form, allows the filling of the compressor by its gas and the control of this filling. Outside the enclosure, this stainless steel pipe could be prolonged by a brass tube allowing connection to the gas tank by using methods usual to cooling technicians.

Constituting parts of the water loop heat pump core as just described are grouped inside an enclosure 40 itself built of two parts: a supporting base 41 and a bonnet 42. Favourably, all useful inlets and outlets and all accesses to the parts of the heat pump core are grouped on the supporting base 41, notably inlets 23, 33 and outlets 24, 34 to and from harnessing and heating loops. Are also located on the supporting base 41, the crossing 43 for the electric line feeding the motor of the compressor 11, as well as an occlusive aperture allowing communication with the internal free volume of the enclosure when the bonnet 42 is closed, and a crossing 45 for the tube 16 to introduce or control the gas of the compressor. In FIG. 1 the supporting base extends across the whole lower part of the assembly. However it may as well extend across whole or a part of any side or of certain sides of the assembly, according to the needs when designing the heat pump.

The bonnet 42 can thus easily be tighten, since it is of one piece only, for instance of thin metal, without any crossing. It can be sealed tighten to the supporting base 41 in order to form a tighten enclosure around the heat pump core. When the bonnet and the supporting base are both of metal, this sealing can even favourably be performed by welding of these two parts together presenting then an un-dissociable functional unit. Other means of permanent sealing can be considered, for instance by gluing, when bonnet and/or supporting base are not of metal possibly welded.

Favourably, after sealing of the enclosure, through aperture 44 is introduced an isolating material that fill all the internal free volume of the enclosure, for instance appropriate powder or expanding foam, that will minimise parasitic thermal exchanges and thus increase the performance of the equipment. Moreover, this filling reduces the transmission of mechanical and acoustic vibrations from the compressor to outside.

After filling, vacuum can be applied to the tighten enclosure or it can be filled by a dry gas bringing thermal insulation better than air, for instance argon or sulphur hexafluoride.

Finally, should the supporting base constitutes the lower side, and insofar as pipes 26 and 36 reaching the highest point of harnessing and heating circuits, are straight and not bent, it is possible to slip inside bleed-taps composed of an automatic bleed-tap 46 supported by a pipe 48 with at its lower part, outside the enclosure 40, an aperture 50 on a coupler screwed or otherwise tightly attached to the opening outside of the pipes 26 or 36.

These bleed-taps, placed from outside (as shown on the drawing), can easily be replaced afterwards, if necessary. 

1. A water loop heat pump core comprising a compressor assembly (10), comprising a closed circuit of cooling gas with a compressor (11), a condenser (13), an expander (14) and a vaporiser (12), an inlet (23) and an outlet (24) from and to a harnessing loop, an inlet (33) and an outlet (34) from and to a heating loop, a first heat exchanger (20), coupled on its primary side to the vaporiser of the compressor assembly and on its secondary side to the inlet and outlet of the harnessing loop, and a second heat exchanger (30), coupled on its primary side to the condenser of the compressor assembly and on its secondary side to the inlet and outlet of the heating loop, characterised in that the linking pipes (21, 22, 31, 32) between the heat exchangers and the compressor assembly, and/or the linking pipes (25, 26, 35, 36) between the heat exchangers and the inlets and outlets of the harnessing and heating loops, are non-brazed linking pipes which are made from welded stainless steel pipes.
 2. The heat pump core of claim 1, wherein the stainless steel pipes are welded by orbital TIG welding.
 3. The heat pump core of claim 1, wherein the heat exchangers (20, 30) are stainless steel tubular exchangers.
 4. The heat pump core of claim 1, wherein the compressor assembly, the heat exchangers, the linking pipes between the exchangers and the compressor assembly, and between the exchangers and the inlets and outlets of the harnessing and heating loops, are enclosed inside a tight containment enclosure (40).
 5. The heat pump core of claim 1, wherein the exchangers are essentially without support brackets for attaching them to the supporting frame.
 6. The heat pump core of claim 1, wherein the containment enclosure (40) comprises a supporting base (41) forming at least part of at least one side of the assembly, supporting the compressor assembly and the heat exchangers, and a bonnet (42) mounted onto said supporting base.
 7. The heat pump core of claim 6, wherein the supporting base (41) and the bonnet (42) are attached together in a permanent manner.
 8. The heat pump core of claim 6, wherein the remaining free space inside the containment enclosure is filled with an insulating material, and the supporting base (41) includes an occlusive aperture (44) to introduce said insulating material.
 9. The heat pump core of claim 6, wherein vacuum has been applied to the internal atmosphere of the containment enclosure, and the supporting base (41) includes an occlusive aperture (44) in communication with said atmosphere to apply said vacuum.
 10. The heat pump core of claim 6, wherein the internal atmosphere of the containment enclosure is filled with a dry insulating gas, and the supporting base (41) includes an occlusive aperture (44) in communication with said atmosphere to introduce said gas.
 11. The heat pump core of claim 8, wherein the inlets and outlets (23, 24) of the harnessing loop and the inlets and outlets (24, 34) of the heating loop, and said occlusive aperture(s) (44) are all grouped on said supporting base (41).
 12. A heat pump, characterised by including, in combination: a pump heart according to claim 1, coupling members, including at least one circulating pump, to a harnessing loop, coupling members, including at least one circulating pump, to a heating loop, thermal regulating means, and means for supplying electricity to the assembly. 